The invention relates to a slide gate valve having a cementless joint between the valve and the discharge tap of a metallurgical vessel, such as a steel converter. The invention is particularly adapted for use with a slide gate valve of the type comprising at least one fixed refractory plate having a flow opening disposed generally in alignment with the tap opening, at least one movable refractory plate having a flow opening, means such as an air cylinder for displacing the movable plate with respect to the fixed plate in order to control a flow of liquid metal by controlling the overlap of the respective flow openings in the fixed plate and movable plates, and means for compressing the movable plate against the fixed plate to provide both static and dynamic seals between the plates.
Slide gate valves of this type are known. In most of these, the fixed plate of the gate valve is cemented to the end of the discharge tap, which end is located outside of the metallurgical vessel. For this purpose, the end of the tap is coated with cement, and the fixed plate is pressed against the tap end.
Due to the erosion of the refractory plates, principally as a result of the sliding valve movements, it is necessary to periodically replace the refractory plates. Such replacement requires destruction of the cement joint, followed by cleaning of the exterior face of the tap to remove the cement which has served to affix the used plate being replaced. Generally, a hammer and chisel are employed for this cleaning. Finally, one must produce a new cement joint to affix the new plate to the tap opening.
This known method is beset by a number of drawbacks. The conditions under which workers must work to clean the exterior face of the tap opening are stressfully hot. In general, it is not possible to effectively cool the metallurgical vessel because such cooling would take inordinate time, which would be chargeable as downtime of the vessel. Further, the cleaning of the tap entails the risk of damage to the opening, which would reduce its useful life. Moreover, after the cement for the new joint has been applied, it is necessary that the opening in the fixed plate be quickly and accurately emplaced on the tap on the first attempt since the cement sets rapidly in the presence of the high temperature of the discharge tap. If the plate is wrongly positioned, the joint must be completely reformed (i.e., broken up, cleaned, and recemented).
These drawbacks are aggravated in the case of converters, for which an interruption entails lost production. Thus there is a need to minimize the time required for cleaning. This aggravates the stressful working conditions, particularly since the dimensions of the gate valve on converters are much greater than those of valves on other vessels (e.g., ladles and tundishes), and since a converter, in contrast to other vessels, cannot be moved away from the operating environment.
A gate valve is also disclosed in French Patent 2,436,923 which is provided with a closure plate that is solid and bears an opening for passage of the metal. This closure plate is disposed between two other plates, an upper plate and a lower support plate to which a discharge nozzle or tube is affixed. In a device of this type, the upper plate is the operating plate, in that with each sliding movement of the closure plate, the closure plate rubs against the lower face of the upper plate. Accordingly, the lower face of the upper plate is eroded relatively rapidly, which necessitates that the upper plate be replaced each time the closure plate is changed.